$\begingroup$Psi-pounds of pressure per square inch. For the calculations and a good explanation google the page "pressure increase due to thermal expansion @Eng-tips.com engineering forums.$\endgroup$
– TechnetiumNov 26 '15 at 6:02

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$\begingroup$The ideal gas law - PV=NRT=mRT should be able to be used here.$\endgroup$
– TechnetiumNov 26 '15 at 9:11

$\begingroup$Strictly speaking, you don't even need to know what psi is. Just apply the ideal gas law and return your answer in the same units.$\endgroup$
– Ivan NeretinDec 1 '16 at 9:21

$\begingroup$Be careful here, the constant R has many values, some of which works with psi. But yea, apply ideal gas law with the appropriate R and you don't need to concern yourself with psi. R is approximately 5.961 ft3 psi K^-1 lb-mol^-1$\endgroup$
– Stian YttervikDec 1 '16 at 12:16